A new technology makes it possible to use a sealed-off CO2 laser to produce high-quality markings directly on the glass. This is a technology that can replace expensive solid-state lasers and traditional glass marking methods (25W CO2 lasers can meet most of the requirements for marking on glass). CO2 lasers mark the glass by destroying the glass surface, so a certain amount of cracks on the glass is allowed, but excessive cracks may cause unclear marks, potential weakening of the material strength, and more seriously the substrate becomes Loosening, precisely controlling the amount of cracks in the material during the marking process can avoid these problems.
There are three ways to control the type and number of cracks on the glass surface:
The first method uses multiple times of China Perfect laser radiation; the second method uses discrete points to form a ring-shaped crack; the third method is to produce a crack-like surface crack. A single laser radiation produces a sharp visible mark on the glass, but the direction of the crack and stress pattern will expand perpendicular to the direction of laser movement. After a short time or even a few days after the mark is printed, these cracks perpendicular to the direction of laser light will form new cracks, extending to the vicinity of the original mark to form fragments, thereby affecting the sharpness of the mark. By using multiple times of China Perfect laser radiation, the areas adjacent to the marked areas are heated by heat conduction, thereby forming stress gradients in these areas, reducing the possibility of secondary cracking. Marking on soda lime glass and borosilicate glass using this method is very effective. One laser radiation is more effective in marking on fused silica glass and quartz glass because the expansion coefficients of the two materials are very low.
Using a series of annular cracks to form text, bar codes, square or rectangular codes, and other shape code patterns. The glass produces a low density annular crack through heating and cooling cycles. When the glass is heated, it expands to compress the surrounding material. When the temperature rises to the softening point of the glass, the glass rapidly expands to form a dome of the convex glass surface of the low-density material. After heating, the glass shrinks to the original surface position, but this relaxation time is the time during which the entire low density is formed, making it impossible to return to the starting position before the softening temperature.
Three different marking methods were used to mark the glass with a CO2 laser, that is, multiple laser passes; discrete points formed annular cracks and cracked surface cracks.
Since the spot energy is Gaussian, the temperature at the center of the spot is high. When this high temperature region returns to near the starting position, the center of the annular crack is formed in this region. A stable annular crack is formed at the joint between the low density forming region and the standard density region. This method is suitable for marking on ordinary optical materials and tempered glass, chemically reinforced glass or ordinary soda lime float glass.